Recent developments in microfabrication techniques (also called micromachining), applicable to discrete semiconductors and to integrated circuits (ICs), have brought vast changes to the electronics industries, and have focused attention on smaller, more efficient devices capable of large-scale production at low cost. More particularly, micromachining includes the techniques of planar technology, wet chemical etching and other etching techniques, metallization, and metal deposition. Planar technology includes the various techniques used in integrated circuit fabrication, such as photolithography, oxide etching, thermal diffusion, ion implantation, chemical vapor deposition, and dry plasma etching.
The present inventive concept includes a basic microminiature electrical element and its multiple uses, and the method of manufacture thereof. Micromechanical voltage controlled switches and microsized resonant elements have become known and experimentally tested in certain uses, including as matrix-addressed, optical image storage devices, inexpensive displays, ac signal switching arrays, as reactive (especially inductive and/or tuned) elements, as microrelays, as microsensors, and as microsized switches in microwave stripline circuits.
In the interim, recognition of the need to develop microsensors and photo-optic fiber and microcomponent communications and control techniques in the process control industries has created an unfulfilled need for development of new similar devices in that industry.
For the purposes of this limited description, "process control" includes both individual variable processes and complex processes involving a large number of controlled process conditions such as fluid flow, flow rate, temperature, pressure, level, and the like. "Shunt" is used in describing the present invention in the sense of providing a lower current pathway connecting two points, which points are not necessarily parallel with another current path. "Station" generally refers to a place, site, base, installation, point, locality, terminal, or post. "Hysteresis" is defined as the lagging of a physical effect on a body behind its cause after the causal force is changed in value or removed.
Industrial process control apparatus and techniques have evolved over a number of years from relatively simple individual variable controllers for separate respective process conditions, to very large integrated systems including sophisticated analog and digital processing equipment and sophisticated communications (telemetering) techniques for remotely communicating the process control signals to and from the site of the process control actuator, often a valve, switch, clutch, brake, solenoid, relay, motor, or servomotor or sensor.
The communications/telemetry process may involve (individually or in combination) pneumatic, electric, optical fiber light path, or various other communications media techniques. Converting the communications data to energy to effect change in the process control variable often involves interfacing various energy and communications techniques. Historically, such systems were large and unwieldly and often used substantial amounts of energy.
Micromechanical voltage-controlled switches lacking the hysteresis effect of the present invention and some related circuits are described by Kurt E. Peterson in an article entitled: "Micromechanical Voltage Controlled Switches and Circuits," purportedly published in 1978 (International Business Machines, Corporate Research Division, San Jose, Calif. 95193). Techniques for fabrication of certain configured cantilevered elements superficially similar to the cantilevered portion of the present invention are disclosed in U.S. Pat. No. 3,620,932; in J. B. Angell, S. C. Terry, and P. W. Barth, "Silicon Micromechanical Devices," Scientific American, Vol. 248, April 1983, pp. 44-55; K. E. Petersen, "Silicon as a Mechanical Material," Proc. IEEE, Vol. 70, No. 5, May 1982, pp. 420-457; and P. W. Barth, "Silicon Sensors Meet Integrated Circuits", CHEMTECH, November 1982, pp. 666-673, all of which are directed to different and inapplicable series of uses. Resonant gate field-effect transistor (RGT) elements are disclosed by Nathanson, et al, in an article entitled: "Tuning Forks Sound a Hopeful Note," Electronics, Sept. 20, 1965, pp. 84-87, and in U.S. Pat. No. 3,600,292 of Aug. 17, 1971, for a method of machining and deposition by sputtering, which method was described as being useful in tuning the vibratory members of RGT's. U.S. Pat. No. 3,796,976 to Heng, et al, describes the use of microsized capacitively coupled switches for in-situ tuning of microwave stripline circuits.